鸡蛋储藏过程中介电特性与新鲜品质的变化

研究了频率在100k～1MHz下无损整蛋介电参数的变化情况,并对介电参数和新鲜品质随储存时间的变化规律进行了探索。结果表明:不同储存天数鸡蛋的相对介电常数值间有显著的差异性;随着储存时间的延长,鸡蛋新鲜度品质指标—蛋黄指数在下降,其中相对介电常数εr′和介质损耗因子Q与蛋黄指数有极显著的相关性。

鸡蛋贮藏过程中的介电特性和新鲜品质变化

依据介电特性检测原理,采用LCR测试仪对常温条件下鸡蛋的介电参数进行检测,同时利用常规破坏性试验,在常温贮藏条件下对鸡蛋进行品质追踪试验,并采用Excel软件对测量数据进行分析和二次曲线拟合。结果表明:鸡蛋的品质参考值哈夫值、失质量率、蛋黄指数与贮藏天数的相关性均显著;鸡蛋的介电参数(Rp)与贮藏时间具有一定相关性;Rp参数与蛋清pH值之间具有负相关性(r<-0.67)。本研究为鸡蛋新鲜品质与介电参数之间相关性的进一步研究提供依据。

水产品新鲜及腐败程度的评价指标

鲜度是判断水产品品质的一项重要指标,水产品的鲜度在很大程度上决定了水产品的价值,因此备受关注。文中简要介绍了水产品鲜度变化,并重点从感官指标、物理指标、化学指标和微生物指标这4个方面介绍了国内外对水产品鲜度的研究现状。

贮藏方式对洁净生菜品质的影响

模拟超市存放条件,探讨了用筒状透明塑料薄膜包裹的生菜在温度为17±2℃、相对湿度为70%和40W荧光灯照射的贮藏条件下其品质变化。结果表明,用筒状透明塑料薄膜包裹的生菜贮藏期间的呼吸强度、相对电导率均低于未包裹的和散堆的生菜,叶绿素、还原糖含量则高于未包裹的和散堆的生菜,抗坏血酸和失重率介于两者之间。

鲜切马铃薯褐变抑制的研究

为了提高鲜切马铃薯的品质,本文通过单因素试验和正交试验分别研究了焦亚硫酸钠、柠檬酸、L-半胱氨酸、CaCl_2、异抗坏血酸钠、EDTA-2Na对马铃薯在鲜切过程中的酶促褐变影响。单因素试验结果表明:抑制马铃薯褐变的试剂的最佳浓度分别是焦亚硫酸钠0.10%,柠檬酸0.20%,L-半胱氨酸0.10%,CaCl_20.10%,异抗坏血酸钠0.10%,EDTA-2Na0.10%;正交试验结果表明:当选取柠檬酸、L-半胱氨酸、CaCl_2、异抗坏血酸钠作为抑制剂和以鲜切马铃薯的最低褐变度为目标值时,经过试验并将其结果进行参数优化获得其最佳方案是:柠檬酸0.40%+L-半胱氨酸0.15%+异抗坏血酸钠0.30%+CaCl_2 0.40%。以此方案进行试验验证,测得样品的平均褐变度仅为0.071,表明该方案可有效抑制马铃薯的酶促褐变,保证鲜切马铃薯的新鲜品质。

Changes of Pectin Quantity in Fresh and Frozen Apple Products

Recently more and more innovations enter the manufacture of food products and one of them is food hydrocolloids. Food colloids open a lot of different possibilities in dessert production, which are used to perform certain functions. Pectin is a traditional agent for jams and jellies, but its application extends to fruit products for the food industry. In food product technology pectin is added as gelling agent and stabilizer. The three apple varieties ＂Antonovka＂, ＂Baltais Dzidrais＂ and ＂Zarja Alatau＂ harvested in Latvia State Institute of Fruit Growing were used for the experiment. Photometric measurement was used to determine the composition of pectin. Pectin was isolated from the apple mass by leaching with ethanol, and from the residues by extracting with diluted sodium hydroxide solution. By adding carbasol and sulphuric acid to the extract, through different intermediate stages carroty condensation product formed, which was photometrically measured at 525 nm. Pectin, pH and soluble dry matter were determined in fresh and frozen apple mass from apples of three ripeness stages. On the basis of worked out functional analysis of colloids, it is possible to optimize regulation of heat processes for different ripeness stages of apples. It is established that ripeness stage influences pectin quantity in fruits, but there are no data about pectin quantity changes in frozen fruits. By fruit ripening under the impact of enzyme protopectinase, protopectin hydrolyzes and transforms into pectin, which flows from the intercellular spaces into protoplasm of cells. Therefore ripe as well as heat treated fruits are soft and loose. It is important to measure pectin in frozen apple mass, in order to determine its potential jellying power. For each kind of product appropriate conditions have to be chosen for freezing, as well as the condition of products before freezing has to be taken into consideration in order to reduce the harmful influence on their quality to the minimum. The results of the research indicate that pectin quantity in frozen apple mass has decreased substantially. This susceptibility of sugar containing products to temperature fluctuations possibly is due to their high concentration of unfrozen water and lower melting temperature. It is possible to calculate the mass fraction of ice depending on temperature and moisture content in product which is very important for prognosticating the product quality. The aim of the research is to compare changes of pectin quantity in fresh and frozen apple products depending on storage time. The research is related to application possibilities of the current colloids, which are used in food industry at present.

粤与凤行 香临凰庭

初见凰庭,底蕴悠远。作为半岛酒店集团落足京城30多年的粤菜餐厅,中国传统古典庭院设计的凰庭低调舒雅。新推零点菜单和点心单以新鲜品质食材为创作本心,如精心选用广东马岗鹅、红花蟹、水牛奶等提升菜点口感。餐厅主厨张永超认为,菜式万变不离其宗,要在坚守传统的基础上,把脉当今口味演变,不断挖掘和创新。厨师团队秉承粤式经典烹饪技艺,依循时令,并将“以热度传递温度”的出品理念融入此次菜品的呈现方式中,于细微处见新意。